500 internal server error viewing MR

We’re just getting started rolling out GitLab and are running through some basic workflows in an instance of CE 8.12.4. We have a case where I forked a repo, committed a change and pushed to my fork, and opened an MR to the upstream. In the MR I assigned it to a Master of the upstream and mentioned a different Master of the upstream in a comment, creating a Todo for Master #2. Master #1 merged the change, and I deleted my fork. Now Master #2 is back and sees the Todo. Clicking on it, he receives a “500 internal server error” page. Nagivating to the upsteam repo > Merge Requests > Merged we can see the MR listed. but clicking on it gives us all the 500 error. I don’t see anything in the logs other than the nginx log/

I searched on google MR #152 posted to the gitlab-org/gitlab-ce project.

Ironically, the title is “Fixed 500 internal server error for MRs with missing source” and when I click on it, I am given a 500 internal server error …

Regression? PEBKAC?

This was already reported and triaged as a bug